Hi,
Hope you are doing well.
1,Per my experience, this is expected behavior. If the computer record already exists, it isn't an "UnknowN" computer anymore, and therefore the task sequence deployed to unknown computers isn't available for it. Because the client is recognized as an known client and no optional advertisement for it. We can check this in the smspxe.log on the server.
When the PXE server receives the PXE request, it (the PXE server, not the client itself) interacts the client's MAC address and SMSBIOS with the MP to see if the client is in the ConfigMgr Database. If it isn't in the database, the client will be recognized as an unknown computer. So that the PXE server decides if there is a suitable deployment and optional advertisement for the unknown\known client.
When an unknown computer is started, Configuration Manager recognizes the computer as an unprovisioned computer rather than an unknown computer. This means that the computer can now receive the task sequences that were deployed to the unknown computer object. The deployed task sequence then installs an operating system image that must include the Configuration Manager client.
2,As you have also deployed the Windows 11 task sequence to your Windows 10 collection, you can also try to clear PXE flag to have a try.
CM: Delving into the "Last PXE Advertisement" flag
client records and multiple PXE boots
Please note: The links are not from Microsoft, just for your reference.
Hope I have explained this question clearly. Thanks for your time.
Best regards,
Simon
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